This invention relates to pressurized dispensers in general and more particularly to a valve assembly for use with a pressurized container. The valve assembly of this invention allows pressure filling of a container with propellant after the assembly has been engaged with the container and prevents contamination of the material to be dispensed and corrosion of the valve assembly housing.
Generally, pressurized containers comprise a can or bottle containing the material to be dispensed (hereinafter "product") along with a pressurizing fluid, either a valve or a pump, and a mounting cup by means of which the valve or pump is mounted on top of the can or bottle. Generally, in a valve type arrangement, the pressurizing fluid is a liquid propellant, whereas in a pump type arrangement, nitrogen or compressed gas is used. Typically, in a valve type arrangement, a valve for dispensing the product may be crimped into the mounting cup with a diaphragm disposed between the top of the valve body and the mounting cup for sealing around the valve stem and the top of the valve body.
In general, two types of aerosol valves are in common use. They are a metering valve and a non-metering valve. The construction of the metering valve is such that a chamber is formed in the valve body. The chamber is of a size to hold a metered dose of the product to be dispensed. When the valve is in an unoperated position, the tank formed in the valve body is placed in communication with a dip tube extending to the bottom of the can and the tank is filled with the product to be dispensed under pressure. Upon the depression of the valve stem, the inlet from this dip tube and, thus from the container, is closed off and an outlet through the upper part of the stem is then opened. The material under pressure in the tank is forced out through the dispensing outlet. In a nonmetering valve, on the other hand, the tank is always in communication with the dip tube and thus with the container. As a result, depressing the valve to place the outlet in communication with the tank permits a continuous dispensing of the product.
Generally, there are two methods for getting propellant into the container to pressurize the product. One method is cold filling in which the propellant is maintained in its liquid state by cooling and is filled into the container in the liquid state. This, of course, requires special refrigeration equipment to maintain the container and the propellant at a low temperature until the mounting cup and the valve therein can be crimped in place on top of the container. Cold filling, in addition to being complex and expensive, is not at all practical in some cases and may even be dangerous, especially when using hydrocarbon propellants. A certain amount of propellant will escape and collect during cold filling thereby causing a potentially explosive danger when a hydrocarbon such as butane is used as propellant.
Another method of filling, to which this invention is more particularly directed, is known as press re filling. In this method of filling, which is disclosed in my prior U.S. Pat. No. 4,271,875, the propellant is forced into the container, generally through the dispensing outlet in the valve stem. The rate of dispensing from the valve is normally controlled by an orifice or outlet port in the stem. If pressure filling must take place through the orifice, it will take a long period of time. Thus, various methods of achieving fast pressure filling have been developed. For example, sealing ring or diaphragm may be disposed about the outlet port such as disclosed in British Pat. No. 1,287,126. In this arrangement for pressure filling, openings are located at the top edge of the valve body. Normally these holes are covered by the sealing ring or diaphragm at the top of the valve body by means of which the valve is sealed to the mounting cup. In this method of pressure filling, the propellant, after it reaches the tank, forces its way under the sealing ring and finds its way to the holes whereupon it reaches the container.
One known dispenser to which the present invention is particularly suited is adapted for fast pressure filling as discussed above and includes a valve assembly comprising a mounting cup which is adapted to be sealingly and fixingly secured to a container. The mounting cup further defines a central opening through which a discharge plunger may pass, the plunger having restricted axial movement relative to the mounting cup. The plunger has an upper portion which has an axially extending bore terminating in an outlet. The lower end of the axial bore communicates with a radially directed port which extends to the outer circumference of the upper plunger portion.
The plunger also has a lower portion joined to an inner end of the upper portion and extending within the mounting cup. The lower portion containing one or more slots along a portion of its length, beginning from the end of the lower plunger portion furthest away from the upper plunger portion.
The lower plunger portion extends into a metering tan which is in sealing contact with the mounting cup. The metering tank has an opening at its inner end with the inner end of the plunger extending through this opening and out of the metering tank. The metering tank includes at least one axial port extending through its walls which communicates with a space formed between the metering tank and the plunger. A fluid tight seal is formed over this port by an elastic, extendable rubber band-like seal member. The valve assembly further comprises a drainage tank having an open end placed over the metering tank and the lower plunger portion subassembly.
Containers such as those described above often contain parts which are formed from a metal, such as the valve assembly housing which may be formed from stainless steel and the mounting cup which maybe formed from aluminum. Due to the arrangement of the housing over the container filler opening, the housing will often be contacted by the product contained within the container. Since some of these products have a tendency to attack and or corrode the metal housing (e.g., medications which are acidic are known to corrode aluminum in the presence of moisture) the product contained in prior dispensers may become contaminated and the quality of the seal between the housing and the container may degrade.
It is therefore an object of the present invention to provide a valve assembly which prevents contamination of the product and is not subject to chemical attack by the product.
Another object of this invention to provide an improved pressure filling valve which will expand upon connection to a source of pressurized fluid thereby permitting propellant to flow into the container and pressurize the product, yet at the same time remain in its sealing location to ensure proper closing of the valve after pressure filling is completed and the source is disconnected.
These and other objects of the present invention will become apparent from the following description an claims in combination with the drawings.